Synthesis of Ethyl Esters from Waste Cooking Oil Using a Calcined Coconut Husk-Based Catalyst: A Novel Green Approach

Abstract

A low-cost heterogeneous base catalyst was prepared by simple calcination of coconut husk at 700°C and applied to the ethanolysis of Waste Cooking Oil (WCO). The catalyst was characterised by FTIR, XRD, SEM and nitrogen physisorption, revealing a silica-rich matrix containing crystalline quartz, potassium chloride and residual graphitic carbon together with a BET surface area of 181.9 m2 g-1 and a modal pore diameter of 3.0 nm. Response-surface methodology with a central-composite design was used to optimise reaction time, ethanol-to-oil molar ratio and catalyst loading. Under the statistically derived optimum conditions (53.3 min, 5.96: 1 ethanol-to-oil ratio and 2.23 wt % catalyst) an ethyl-ester yield of 83.9 % was obtained, in close agreement with the model prediction. The product satisfied the key ASTM D6751 limits for density, viscosity, acid value, flash point, cetane number and iodine value. The work demonstrates that an unmodified, waste-derived ash catalyst can drive the conversion of high-FFA waste oil to ethyl esters without chemical impregnation or toxic reagents, thereby offering a genuinely green dual-waste valorisation route for biodiesel production.

Keywords: Waste Cooking Oil; Ethyl Esters; Coconut-Husk Ash; Heterogeneous Base Catalyst; Response-Surface Methodology; Green Biodiesel

Citation

Daniel UI, Wisdom CU, Emmanuel TE, Emmanuel D, Cyril OA, David RI. Synthesis of Ethyl Esters from Waste Cooking Oil Using a Calcined Coconut Husk-Based Catalyst: A Novel Green Approach. WebLog J Chem Eng. wjche.2026.j2104. https://doi.org/10.5281/zenodo.23611918